I wanted to do long range telemetry so I got myself a dipole antenna for the modem. 

I never could check the range because the plane couldn't get a gps lock anymore, with the modem powered on. With the modem powered off, I had a 3D GPS lock, 17 sats in seconds.

What can I do to get both long range telemetry and good GPS?

Views: 2858

Reply to This

Replies to This Discussion

Can you add a picture of your hb antenna? Or a link to the tutorial on how to make it? And a parts list?

I was thinking of DIY 4 elements yagi antenna for the GCS. Would that work?

Did you ever fly beyond 20 km?

Thanks,

Anton.

The hb antenna is basically the coax from which I removed the shielding for L/4 165mm (so 300/433/4*.95), at the point where the shielding stops a soldered a wire of the same length. The antenna is taped on the tail of the plane and vertical polarized.

My TX/RX is not shielded and close to the GPS receiver, the antenna feed coax runs over the GPS receiver. I did not experienced any drawback in GPS performance. On the picture with the RX/TX you can see the ferrites around the coax feed and signal wires.

Yes you can use a 4el Yagi, but you have to point it towards your plane, my Diamond X5000 antenna has full round radiation pattern in a shape of a "pancake" with 8dBi gain. So my antenna is fixed at the roof of my house. Height of he antenna is key!!!

After several long distance experiments my main conclusions where: Avoid man made disturbance (select empty frequency), Antenna height, Plane antenna far from other electronics.

No beyond 20Km I did not go, the "distanceRSSIremain" showed over 100Km reserve, but I doubt if the rounding of the earth is taken in account .

I'm currently experimenting with a video camera in the plane and a FM link at 1296MHz, also here my goal is 20Km, but here I use an rotated 55el vertical Yagi at 20m height. This test is not finished due lack of time and good weather.  

Hi Anton.

I don't post often but have been a member here for many years. Please take the time to consider the advice of  Gisela and Joe. I have never directly needed their advice but have a great respect for their methodical problem solving skills. I have however been an engineer for 39 years and their method is a tried and tested one.

Regards Lyn. 

OK I solved it! Thanks everyone - and especially Joe - for your suggestions. Powering the modem via a separate UBEC - like Joe suggested - worked like magic. No balun needed, no ferrite core. 

The modem came with a little 4 wire cable that became a 6 wire plug at the autopilot side. I removed the red wire from that socket by lifting the little plastic finger keeping it in place. I then soldered a hitec female connector to the red wire. Next I cut the black wire and made three way junction, one continuing to the autopilot, the other to hitec. My UBEC had a hitec male connector. I forgot to add the ferrite core again, but it worked so I didn't bother. 

I suppose moving the dipole to the tail and making it a half wavelength dipole would be even better, I could then move the GPS & Rx to the front. But I didn't have the right cables and mounting surfaces to do that. And this just worked.

Here's an update overview of my tries. If you have more questions, just ask!

Reply to Discussion

RSS

Groups

Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Vertical Horizontal one, is here

© 2017   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service